People (including me) pay for things in advance all the time here on the honor system, so that's reasonable, IMO
ive done THAT for people, too. no problem. but if you don't get money, you get flakes. i'd say easily 8 out of 10 people i've held things for, without pre-payment, have backed out. in fact, i think i'm being generous with that... cause i cant actually remember a time when i've held something for somebody and they've actually followed through.